ch01_an overview of computers and programming languages

C++ PROGRAMMING
FROM
PROBLEM ANALYSIS TO
PROGRAM DESIGN
SEVENTH EDITION
Chapter 1:
An Overview of Computer and
Programming Languages

OBJECTIVES
 In this chapter, you will:
 Learn about different types of computers
 Explore the hardware and software components of a
computer system
 Learn about the language of a computer
 Learn about the evolution of programming languages
 Examine high-level programming languages
2
C++Programming:FromProblemAnalysis
toProgramDesign,SeventhEdition

OBJECTIVES (CONT’D.)
 Discover what a compiler is and what it does
 Examine a C++ program
 Explore how a C++ program is processed
 Learn what an algorithm is and explore problem-solving
techniques
 Become aware of structured design and object-oriented
design programming methodologies
 Become aware of Standard C++, ANSI/ISO Standard C++, and
C++11
3
C++ Programming: From Problem Analysis to Program Design, Seventh Edition

INTRODUCTION
 Without software, the computer is useless
 Software is developed with programming languages
 C++ is a programming language
 C++ suited for a wide variety of programming tasks
4

A BRIEF OVERVIEW OF THE HISTORY OF
COMPUTERS
 Early calculation devices
 Abacus, Pascaline
 Leibniz device
 Jacquard’s weaving looms
 Babbage machines: difference and analytic engines
 Hollerith machine
5

COMPUTERS (CONT’D.)
 Early computer-like machines
 Mark I
 ENIAC
 Von Neumann architecture
 UNIVAC
 Transistors and microprocessors
6

COMPUTERS (CONT’D.)
 Categories of computers
 Mainframe computers
 Midsize computers
 Micro computers (personal computers)
7

ELEMENTS OF A COMPUTER SYSTEM
 Hardware
 CPU
 Main memory
 Secondary storage
 Input/Output devices
 Software
8

HARDWARE
 CPU
 Main memory: RAM
 Input/output devices
 Secondary storage
9

CENTRAL PROCESSING UNIT AND MAIN
MEMORY
 Central processing unit
 Brain of the computer
 Most expensive piece of hardware
 Carries out arithmetic and logical operations
10

MEMORY (CONT’D.)
11

MEMORY (CONT’D.)
 Random access memory
 Directly connected to the CPU
 All programs must be loaded into main memory before they can
be executed
 All data must be brought into main memory before it can be
manipulated
 When computer power is turned off, everything in main memory
is lost
12

MEMORY (CONT’D.)
 Main memory is an ordered sequence of memory cells
 Each cell has a unique location in main memory, called the
address of the cell
 Each cell can contain either a programming instruction or data
13

SECONDARY STORAGE
 Secondary storage: device that stores information permanently
 Examples of secondary storage:
 Hard disks
 Flash drives
 Floppy disks
 Zip disks
 CD-ROMs
 Tapes
14

INPUT/OUTPUT DEVICES
 Input devices feed data and programs into computers
 Keyboard
 Mouse
 Secondary storage
 Output devices display results
 Monitor
 Printer
 Secondary storage
15

SOFTWARE
• Software: programs that do specific tasks
• System programs control the computer
– Operating system monitors the overall
activity of the computer and provides
services such as:
• Memory management
• Input/output activities
• Storage management
• Application programs perform a specific task
– Word processors
– Spreadsheets
– Games
16

THE LANGUAGE OF A COMPUTER
 Analog signals: continuous wave forms
 Digital signals: sequences of 0s and 1s
 Machine language: language of a computer; a sequence of 0s
and 1s
 Binary digit (bit): the digit 0 or 1
 Binary code (binary number): a sequence of 0s
and 1s
17

(CONT’D.)
 Byte:
 A sequence of eight bits
 Kilobyte (KB): 210
bytes = 1024 bytes
 ASCII (American Standard Code for Information Interchange)
 128 characters
 A is encoded as 1000001 (66th character)
 3 is encoded as 0110011
18

(CONT’D.)
19

(CONT’D.)
 EBCDIC
 Used by IBM
 256 characters
 Unicode
 65536 characters
 Two bytes are needed to store a character
20

THE EVOLUTION OF PROGRAMMING
LANGUAGES
 Early computers were programmed in machine language
 To calculate wages = rate * hours in machine language:
100100 010001 //Load
100110 010010 //Multiply
100010 010011 //Store
21

LANGUAGES (CONT’D.)
 Assembly language instructions are mnemonic
 Assembler: translates a program written in assembly language
into machine language
 Using assembly language instructions, wages = rate •
hours can be written as:
LOAD rate
MULT hour
STOR wages
22

LANGUAGES (CONT’D.)
 High-level languages include Basic, FORTRAN, COBOL, Pascal, C,
C++, C#, and Java
 Compiler: translates a program written in a high-level language
into machine language
 The equation wages = rate • hours can be written in C++
as:
wages = rate * hours;
23

PROCESSING A C++ PROGRAM
#include <iostream>
using namespace std;
int main()
{
cout << "My first C++ program." << endl;
return 0;
}
Sample Run:
My first C++ program.
24

(CONT’D.)
 To execute a C++ program:
 Use an editor to create a source program in C++
 Preprocessor directives begin with # and are processed by the
preprocessor
 Use the compiler to:
 Check that the program obeys the language rules
 Translate into machine language (object program)
25

(CONT’D.)
 To execute a C++ program (cont'd.):
 Linker:
 Combines object program with other programs provided by the SDK to
create executable code
 Library: contains prewritten code you can use
 Loader:
 Loads executable program into main memory
 The last step is to execute the program
 Some IDEs do all this with a Build or Rebuild command
26

(CONT’D.)
27

PROGRAMMING WITH THE PROBLEM
ANALYSIS–CODING–EXECUTION CYCLE
 Algorithm:
 Step-by-step problem-solving process
 Solution achieved in finite amount of
time
 Programming is a process of problem
solving
28

THE PROBLEM ANALYSIS–CODING–
EXECUTION CYCLE (CONT’D.)
 Step 1: Analyze the problem
 Outline the problem and its requirements
 Design steps (algorithm) to solve the problem
 Step 2: Implement the algorithm
 Implement the algorithm in code
 Verify that the algorithm works
 Step 3: Maintain
 Use and modify the program if the problem domain changes
29

 Thoroughly understand the problem and all
requirements
 Does program require user interaction?
 Does program manipulate data?
 What is the output?
 If the problem is complex, divide it into subproblems
 Analyze and design algorithms for each subproblem
 Check the correctness of algorithm
 Can test using sample data
 Some mathematical analysis might be required
30

 Once the algorithm is designed and correctness verified
 Write the equivalent code in high-level language
 Enter the program using text editor
31

 Run code through compiler
 If compiler generates errors
 Look at code and remove errors
 Run code again through compiler
 If there are no syntax errors
 Compiler generates equivalent machine code
 Linker links machine code with system resources
32

 Once compiled and linked, loader can place program into main
memory for execution
 The final step is to execute the program
 Compiler guarantees that the program follows the rules of the
language
 Does not guarantee that the program will run correctly
33

EXAMPLE 1-1
 Design an algorithm to find the perimeter and area of a rectangle
 The perimeter and area of the rectangle are given by the
following formulas:
perimeter = 2 * (length + width)
area = length * width
34

EXAMPLE 1-1 (CONT’D.)
 Algorithm:
 Get length of the rectangle
 Get width of the rectangle
 Find the perimeter using the following equation:
perimeter = 2 * (length + width)
 Find the area using the following equation:
area = length * width
35

EXAMPLE 1-5
 Calculate each student’s grade
 10 students in a class; each student has taken five tests;
each test is worth 100 points
 Design algorithms to:
 Calculate the grade for each student and class average
 Find the average test score
 Determine the grade
 Data: students’ names; test scores
36

 Algorithm to determine the average test score:
 Get the five test scores
 Add the five test scores
 Suppose sum stands for the sum of the test scores
 Suppose average stands for the average test score:
 average = sum / 5;
37

 Algorithm to determine the grade:
if average is greater than or equal to 90
grade = A
otherwise
if average is greater than or equal to 80 and less than
90
grade = B
otherwise
80
grade = C
otherwise
70
grade = D
otherwise
grade = F 38

 Main algorithm is as follows:
 totalAverage = 0;
 Repeat the following for each student:
 Get student’s name
 Use the algorithm to find the average test score
 Use the algorithm to find the grade
 Update totalAverage by adding current student’s average test score
 Determine the class average as follows:
 classAverage = totalAverage / 10
39

PROGRAMMING METHODOLOGIES
 Two popular approaches to programming design
 Structured
 Object-oriented
40

STRUCTURED PROGRAMMING
 Structured design:
 Dividing a problem into smaller subproblems
 Structured programming:
 Implementing a structured design
 The structured design approach is also called:
 Top-down (or bottom-up) design
 Stepwise refinement
 Modular programming
41

OBJECT-ORIENTED PROGRAMMING
 Object-oriented design (OOD)
 Identify components called objects
 Determine how objects interact with each other
 Specify relevant data and possible operations to be performed on
that data
 Each object consists of data and operations on that data
42

(CONT’D.)
 An object combines data and operations on the data into a single
unit
 A programming language that implements OOD is called an
object-oriented programming (OOP) language
 Must learn how to represent data in computer memory, how to
manipulate data, and how to implement operations
43

(CONT’D.)
 Write algorithms and implement them in a programming
language
 Use functions to implement algorithms
 Learn how to combine data and operations on the data into a
single unit called an object
 C++ was designed to implement OOD
 OOD is used with structured design
44

ANSI/ISO STANDARD C++
 C++ evolved from C
 C++ designed by Bjarne Stroustrup at Bell Laboratories in early
1980s
 Many different C++ compilers were available
 C++ programs were not always portable from one compiler to
another
 In mid-1998, ANSI/ISO C++ language standards were approved
 Second standard called C++11 approved in 2011
45

SUMMARY
 Computer: electronic device that can perform arithmetic and
logical operations
 Computer system has hardware/software
 Central processing unit (CPU): brain
 Primary storage (MM) is volatile; secondary storage (e.g., disk)
is permanent
 Operating system monitors overall activity of the computer
and provides services
 Various kinds of languages
46

SUMMARY (CONT’D.)
 Compiler: translates high-level language into machine code
 Algorithm: step-by-step problem-solving process; solution in finite
amount of time
 Problem-solving process has three steps:
 Analyze problem and design an algorithm
 Implement the algorithm in code
 Maintain the program
47

SUMMARY (CONT’D.)
 Structured design:
 Problem is divided into smaller subproblems
 Each subproblem is solved
 Combine solutions to all subproblems
 Object-oriented design (OOD): a program is a collection of
interacting objects
 Object: data and operations on those data
48

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